1. Technical Field of the Invention
The present invention relates to a device and a method for setting an add signal level for an OADM (Optical Add-Drop Multiplexer) system, and specifically relates to a device and a method for an OADM system for setting a power of add signal light according to optical powers of individual wavelengths of an input wavelength division multiplexed signal in an OADM system for wavelength division multiplexed transmission.
2. Description of the Prior Art
FIG. 1 shows an example of a conventional OADM system. The conventional OADM system 50 is constituted while including a demultiplexer 51 for demultiplexing a wavelength division multiplexed signal into individual waves, optical switches 52 (52-1 to 52-n: n is a positive integer) for selecting whether adding a signal from outside or dropping the signal to outside, level monitors 53 (53-1 to 53-n) for monitoring levels of the individual optical signals, optical level controllers 54 (54-1 to 54-n) for controlling the levels of individual optical signals, and a multiplexer 55 for multiplexing the individual optical signals after the level control, for example.
The demultiplexer 51 demultiplexes the entire input wavelength division multiplexed signal into the individual waves, the level monitors 53 monitors the levels of all of the add signals and the drop signals, and the optical level controllers 54 control the individual waves such that all of the waves are at the same level.
However, because this method requires the level monitor and the optical level controller for an additional wavelength as the number of multiplexed waves increases, and a circuit scale and the number of parts become large as a result, there is a problem that the cost becomes high, and a failure rate becomes high. Further, the number of through wavelength division multiplexed signals tend to become larger than the number of add optical signals.